(1) Field of the Invention
The present invention relates to a compressor for an air-conditioning system used in a vehicle such as an automobile, more particularly, to a multi-piston swash plate type compressor having a damping arrangement for discharge reed valves therein.
(2) Description of the Related Art
A well known multi-piston swash plate type compressor comprises: a cylinder block body assembled from a pair of cylinder block halves to form a swash plate chamber therebetween, the cylinder block halves having the same number of cylinder bores which are radially formed and arranged with respect to the central axis of the cylinder block body, the cylinder bores of one cylinder block half being aligned and registrated with the cylinder bores of the other cylinder block half, respectively, with the swash plate chamber intervening therebetween; common piston members slidably received in the pairs of aligned cylinder bores, respectively; a swash plate member disposed within the swash plate chamber to be slidably engaged with the common piston members so that the piston members are reciprocated in the pairs of aligned cylinder bores, respectively, by rotation of the swash plate member; a shaft member which extends into an axial bore of the cylinder block body so that it passes through the swash plate chamber and on which the swash plate member is fixedly mounted; a pair of radial bearings provided within the axial bore sections in the cylinder block halves, respectively, for rotatably supporting the shaft member in the axial bore of the cylinder block body; a pair of thrust bearings provided around the shaft member at the sides of the swash plate member; a pair of dish-like housing members mounted on the end faces of the cylinder block body, respectively, so as to form a suction chamber and a discharge chamber between each of the dish-like housing members and the corresponding end face of the cylinder body; and a disc-like reed valve assembly disposed between each of the dish-like housing member and the corresponding end face of the cylinder block body so that each of the cylinder bores is communicated with the corresponding suction and discharge chambers through the intermediary of the corresponding suction and discharge reed valve elements of the disc-like reed valve assembly.
Referring to the disc-like reed valve assembly, in particular, this comprises: an end plate member having sets of a suction port and a discharge port, each set of which is adapted to be communicated with the corresponding cylinder bore; a first valve sheet member disposed between the corresponding end face of the cylinder block body and the inner side surface of the end plate member and having suction reed valve elements formed therein, each of which is arranged so as to open and close the corresponding suction port of the end plate member; a second valve sheet member attached to the outer side surface of the end plate member and having discharge reed valve elements formed therein, each of which is arranged so as to open and close the corresponding discharge port of the end plate member; and a retainer plate member then attached to the second valve sheet member and having retainer elements formed therein, each of which is arranged so as to restrain a lift of the corresponding discharge reed valve element. Note, both the second valve sheet member and the retainer plate member have through holes, each of which is aligned and registrated with the corresponding suction port of the end plate member.
In operation, the shaft member is driven by the engine of a vehicle such as an automobile so that the swash plate member is rotated within the swash plate chamber. The rotational movement of the swash plate chamber causes the piston members to be reciprocated in the pairs of aligned cylinder bores so that the piston members alternately execute a suction stroke and a compression stroke. While each of the piston member executes the suction stroke, the suction reed valve element is opened and the discharge reed valve element is closed, so that a refrigerant is sucked in the cylinder bore from the suction chamber, which is communicated with an evaporator of an air-conditioning system, through the suction port of the end plate member. Then, when the piston member executes the compression stroke, the suction reed valve element is closed and the discharge reed valve element is opened, so that the sucked refrigerant is compressed and discharged into the discharge chamber through the discharge port of the end plate member. As is well known, the refrigerant circulating in the air-conditioning system includes a lubricating oil dispersed there in as a mist. This is intended to ensure that the movable parts of the compressor, such as the radial bearings, the thrust bearings, the swash plate member, etc., are lubricated with the lubricating oil included in the refrigerant during the passage of the refrigerant through the compressor. It is also intended to ensure that an oil layer is formed by the lubricating oil included in the refrigerant between the reed valve element and the valve seat thereof, which corresponds to an annular area surface surrounding the ports of the end plate member. In particular, such an oil layer serves as a damping and sealing layer so that an impact of the reed valve element can be absorbed by the oil layer when the reed valve element impinges against the valve seat, and so that when the reed valve element is closed, it can be effectively sealed against the valve seat due to the existence of the oil.
Note, in the conventional compressor as mentioned above, the retainer elements of the retainer plate member of the disc-like reed valve assembly are arranged to slope away from the surface of the retainer plate member toward a peripheral interior wall surface of the discharge chamber, so that a portion of the discharged refrigerant is guided by the sloped retainer element to flow out toward the peripheral and interior wall surface of the discharge chamber to collide therewith. When the flow of refrigerant collides with the peripheral and interior wall surface of the discharge chamber, the oil mist therein is separated from the refrigerant flow so that oil droplets appear on the peripheral and interior wall surface of the discharge chamber. These oil droplets form an oil flow and thus contribute to formation of the oil layer between the discharge reed valve element and the valve seat thereof. However, in practice, the portion of the discharged refrigerant which is guided by the sloped retainer element to collide with the peripheral and interior wall surface of the discharge chamber is small because a large portion of the discharged refrigerant escapes from opposed triangle side opening zones which are formed between the opposed side edges of the sloped retainer element and the surface of the retainer plate member. Accordingly, it is impossible to obtain a sufficient oil flow which can contribute to the formation of the oil layer between the discharge reed valve element and the valve seat thereof. For this reason, the conventional compressor possesses drawbacks in that the discharge reed valves are damaged because of a poor formation of the oil layer between the discharge reed valve element and the valve seat, and in that it is impossible to obtain an effective oil seal between the discharge reed valve element and the valve seat and thus the compressor operates at a low efficiency.